Depends on what kind of breach and severity. Maybe if the the one breaching laws is harming people and refusing to stop, then maybe a sufficient amount of force by competent entities is required.

Yes

International Law is different from other aspect of law in that it’s a complex system of treaties and conventions and customs. It’s not a monolithic thing.

There question you posed can’t be answered at this level of abstraction.

Can be, depending on circumstances and on the laws.

No